The current mobile communication device has become a pocket-size media center, including a digital camera, an Internet browser, a digital TV receiver, a MP3 player capable of high-fidelity audio playing and five sound tracks Hi-Fi stereo and the like. For the mobile communication device, although the lithium ion battery has been improved, it does not live up to the power amount required for the current mobile communication device. Therefore, how to prolong the working time of the battery for the delicate mobile communication device by using the power management technology is important to the designers of this field.
Referring to FIG. 1, a schematic diagram of a conventional mobile communication device is shown therein. The mobile communication device comprises a processing unit 11 and a battery unit 12. The battery unit 12 provides a power supply and thus a working current 111 to the mobile communication device. The battery unit 12 has to be externally charged to maintain the power therein. When the mobile communication device is carried in hand by a user, it can not be charged through a fixed charging device and the power amount in the battery unit 12 will be totally consumed on the condition that the working current 111 has to be continuously maintained. Finally, the mobile communication device is shut off due to the insufficient power in the battery unit 12, causing apparently trouble and inconvenience to the user. Although another spare battery unit may be charged and then used in the mobile communication device, such power scheme is also not satisfactory due to some reasons. One of the reasons is that the user has to carry the spare battery unit in hand so as to be used for the mobile communication when required. Another reason is that the mobile communication device has to be shut off first and then the original battery unit can be replaced with the spare battery unit. Thus, the inconvenience issue still exists.
To address these problems, the applicant of the present invention envisages that a solar cell unit may be used as the spare battery unit in quest of a prolonged battery time. In addition, the solar cell unit can also provide a luminance value of the ambient environment so as to be shown on a display of the mobile communication device so that the user may be informed of the light quality of the ambient environment, thereby preventing himself/herself from reading under a poor light source environment and thus protecting his/her eyesight from being damaged. According to the above motivations, the present invention sets forth a mobile communication device having the solar cell unit, so as to solve the problems encountered in the prior art.